About Shigella

From the nation’s leading law firm representing victims of Shigella and other foodborne illness outbreaks.

Chapter 6

Complications of Shigella Infection

Reactive Arthritis can be a serious and long-term risk of Shigella infection.

Persons with diarrhea caused by S. sonnei in particular usually recover completely, although it may be several months before their bowel habits are entirely normal. [1, 11, 26] About 2% of persons who are infected with S.flexneri later develop pains in their joints, irritation of the eyes, and painful urination—something typically diagnosed as Reiter’s Syndrome. [1, 6]

Reiter’s syndrome is more generally referred to as reactive arthritis, a complication that accompanies other kinds of bacterial infections as well. [27, 37] This complication occurs because the immune system, intending to fight Shigella, attacks the body instead. [6, 31] Reactive arthritis is most common in persons with the HLA-B27 gene. [31] (About 80% of people with reactive arthritis have the HLA-B27 gene. Only 6% of people who do not have the syndrome have the HLA-B27 gene.) Reactive arthritis can last for months or years and may be difficult to treat. [6]

Once someone has suffered a Shigella infection, a certain level of immunity develops, meaning that the person is not likely to get infected with that specific type again for at least several years. [16] This temporary immunity does not, however, protect against other types of Shigella. [16, 29]

Shigella bacteria multiply in the human intestinal tract and invade the cells, which results in much tissue destruction. [29] Many strains produce a toxin called Shiga toxin, which is very potent and destructive. [16, 22] Shiga toxin is very similar to the verotoxin of E. coli O157:H7. Complications of shigellosis include severe dehydration, seizures in small children, rectal bleeding, and invasion of the blood stream by the bacteria (bacteremia or sepsis). [1, 11, 16, 26] In some cases, the bacteria that cause shigellosis may also cause inflammation of the lining of the rectum (proctitis) or rectal prolapse. [26]

In rare cases (but more common in S. dysenteriae infection), there can also be a deadly complication called “toxic megacolon.” [1, 26] This rare complication occurs when the colon becomes paralyzed, preventing bowel movements or passing gas. [16, 26] Signs and symptoms include abdominal pain and swelling, fever, weakness, and disorientation. [26] Untreated, the colon may rupture and cause peritonitis, a life-threatening condition requiring emergency surgery. [26]

The other relatively rare complication that can occur with a Shigella infection is the development of hemolytic uremic syndrome. This rare complication is more commonly caused by E. coli O157:H7, and it can lead to a low red blood cell count (hemolytic anemia), low platelet count (thrombocytopenia), and acute kidney failure. [26, 37] It is more common to develop HUS after being infected with S.dysenteriae. [1]